The present invention relates to a chuck jaw. More particularly this invention concerns a method of making a drill-chuck jaw with hard-metal inserts as well as a chuck incorporating such jaws.
A standard drill chuck has a body centered on and rotatable about an axis and formed with a plurality of axially extending angled guides angularly spaced about the axis. Respective jaws in these guides can be moved between a forward holding position in which they grip a workpiece and a rear releasing position. Screwthread formations on back edges of the jaws mesh with a threaded sleeve that is rotated relative to the chuck body to advance and retract the jaws. Alternately the guides are formed in a sleeve that rotates relative to the chuck body and the screwthread formations on the jaws mesh with a screwthread on the body for similar action.
Even though the jaws are made of steel, they are typically used to grip tools of similar hardness. Thus it is known to provide special hard-metal, e.g. carbide, inserts in the gripping faces of the jaws to reduce wear of the jaws and thereby prolong the life of the drill or lathe carrying the chuck.
Such inserts must be mounted very, very solidly on the chuck jaws. Once installed they must be able to withstand considerable lateral forces as the chuck applies torque to the tool, and they must hold even when the entire tool gets fairly hot as is common in machining.
It is therefore an object of the present invention to provide an improved method of making an insert-carrying chuck jaw.
Another object is the provision of such an improved method of making an insert-carrying chuck jaw which overcomes the above-given disadvantages, that is which allows the insert or inserts to be mounted very solidly in a cost-efficient and accurate manner.
A further object is to manufacture an insert-carrying chuck jaw where the gripping face of the insert is exactly positioned and not liable to shift during the service life of the chuck.
A drill-chuck jaw according to the invention is made by first forming an elongated metal body with a toothed back face and a front face, then machining a longitudinally extending groove having sides and a floor in the front face, and forming inwardly projecting and longitudinally spaced retaining bumps on the groove sides. A hard-metal insert is fitted into the groove between the retaining bumps and then bonded to the body in the groove. According to the invention the body is heat-treated, that is annealed, before machining the groove in it to reduce internal stresses. Then the body is cleaned and oiled to prepare it for machining and to eliminate any oxidation created by the heat treatment.
Furthermore according to the invention after machining the body and before fitting the insert the body is deburred and cleaned again. This leaves the surfaces of the body clean so that the bonding agent used to secure the inserts can bond directly to the body.
The insert can be bonded to the body with an adhesive. Normally the insert is bonded to the body by soldering or brazing, as such a bond is more resistant to the heat the jaw will be exposed to in use. In order to allow the insert to seat directly on the jaw and not be held off it by the solder a channel is formed between the insert and the body in the groove. The insert is bonded to the body by filling the channel with a bonding agent. The channel can be formed in the insert or in the body.
After bonding the insert to the body, the body is surface hardened, then the body can further be heat treated to increase its strength. More particularly, after bonding the insert to the body, the body is tempered to again eliminate internal stresses. Then it is polished and surface coated to prevent it from rusting.
In accordance with the invention two of the inserts are fitted to the groove at a longitudinal spacing from each other. Furthermore a transversely open blind bore is formed between the inserts and provided with a spring-loaded ball. A retaining ring is fitted to a mouth of the bore to prevent the ball from pushing out of the bore or this ball is held in place by edges of the inserts. This system is particularly usable with a battery-powered drill of the type used with a Phillips bit to set screws, for instance for dry wall. The balls also ensure accurate centering of the tool before the chuck is tightened so that during the tightening operation the jaws perfectly engage the facets of the tool.
The jaws are mounted according to the invention in angled bores of a chuck body, which is then rotated with the jaws about a center axis of the chuck body while engaging a tool with inner edges of the inserts so as to true the inner edges. In this manner the inserts are set perfectly with respect to the chuck body axis. Thus, as is necessary for a hand-tightened chuck, the jaw faces are set perfectly true to the chuck axis, regardless of how wide the chuck is open.